1. Technical Field
The present invention relates to a bearing unit for wheel for supporting a wheel (regardless of a drive wheel or a driven wheel) of an automobile.
2. Description of Related Art
As shown in FIG. 30, a drive shaft 1 for transmitting power from an engine to a drive wheel has a configuration in which a fixed type constant velocity universal joint J1 on an outboard side (a vehicle body side part in a vehicle width direction) and a slidable type constant velocity universal joint J2 on an inboard side (vehicle body center in the vehicle width direction) are connected with an intermediate shaft 2. The constant velocity universal joint J1 on the outboard side is connected to a hub wheel 4 that is supported in a freely rotatable manner by a wheel bearing 3, and the constant velocity universal joint J2 on the inboard side is connected to a differential 5.
The wheel bearing 3 has an inner ring 3a fixed to an outer periphery of the hub wheel 4, an outer ring 3b fixed to a knuckle member 6 that extends from a suspension device on the vehicle body side, and a rolling element 3c arranged in double rows between the inner ring 3a and the outer ring 3b. Normally, the inner ring 3a is fixed to the outer periphery of the hub wheel 4 by being press fit thereinto. The outer ring 3b is usually fixed to the knuckle member 6 by bolting a flange 3b1 of the outer ring 3b to the knuckle member 6.
The conventional drive shaft 1 is assembled to the vehicle by inserting a shaft end on the outboard side (a stem portion 7a of an outer joint member 7) of the drive shaft 1 into an inner periphery of the hub wheel 4 and screw-fitting a nut 8 to the shaft end that projects from the hub wheel 4 with the hub wheel 4 and the wheel bearing 3 being fixed to the knuckle member 6 in advance (see, e.g., Patent Document 1). With tightening of the nut 8, the entire drive shaft 1 slides to the outboard side, and a shoulder portion 7b of the outer joint member 7 contacts an end face of the inner ring 3a. The outer joint member 7 and the hub wheel 4 are thereby positioned in an axial direction, and a predetermined pre-load is applied to the wheel bearing 3. An outer peripheral surface of the stem portion 7a of the outer joint member 7 and an inner peripheral surface of the hub wheel 4 are connected with each other by a spline (not shown), and a drive power of the engine transmitted to the outer joint member 7 is transmitted to the spline, and furthermore, to the wheel via the hub wheel 4.
A pilot portion 4a is formed at the shaft end on the outboard side of the hub wheel 4. Inner peripheral surfaces of a brake rotor 9 and a wheel W are each fitted into the outer peripheral surface of the pilot portion 4a.     [Patent Document 1] Japanese Laid-Open Patent Publication No. 2004-270855